I have a van, and a fan, and some gumption and now I need to start. I have been debating whether to install floor first or insulate first? I plan on using polyiso, assuming I can get some at Home Despot with Great Stuff Pro as described many times I'm these forums and on Gary's buildagreenrv.com site. I also have a fantastic fan to install, using the Impact3d (Hein's) adapter plate. I am wondering if it behooves me to install the fan before the insulation or after? Any suggestions?